CVE-2025-48700: in the CISA KEV catalogue

Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability. CISA added CVE-2025-48700 to the Known Exploited Vulnerabilities catalogue on 2026-04-20 with a default due date of 2026-04-23. Known ransomware campaign use: Unknown. Forensic triage flag: No.

Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability that could allow attackers to execute arbitrary JavaScript within the user's session, potentially leading to unauthorized access to sensitive information. (CISA description)

Vendor / product: Synacor Zimbra Collaboration Suite (ZCS)
CWE: CWE-79
CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
EPSS: 1.7%, percentile 77 (scored 2026-11-03)

EPSS puts about 1.7 in 100 odds (1.7%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 77% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.

Vendor and reference links (from CISA)

Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.

Data dates. CISA KEV catalogue version 2026.11.03, released 2026-11-03, 1,767 entries (checked 2026-11-03). EPSS model v2026.06.15, scored 2026-11-03, 399,388 CVEs. Sources: CISA and FIRST (EPSS by FIRST; scores generated by Empirical Security). Copied to our own database and refreshed automatically; if a refresh fails, the previous copy keeps serving with its own date.

Frequently asked questions

Is CVE-2025-48700 in the CISA KEV catalogue?

Yes. CISA added CVE-2025-48700 (Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2026-04-20. CISA's default due date for it is 2026-04-23.

Is CVE-2025-48700 used in ransomware attacks?

CISA marks known ransomware campaign use as Unknown for CVE-2025-48700. That means CISA lacks confirmation, not that ransomware groups do not use it.

What should I do about CVE-2025-48700?

CISA's required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Sources

CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
NVD record for CVE-2025-48700